The etiology of human prostatic carcinoma remains largely undefined. However, it is becoming clear that epigenetic inactivation of various tumor suppressor genes could play pivotal role in the development of various cancers including prostate cancer. One of such tumor suppressor is Ras- association domain family 1 (RASSF1) gene. Epigenetic inactivation of RASSF1A is probably the most frequently methylated gene described thus far in human cancer. Ectopic expression of RASSF1A in cancer cells that lack endogenous RASSF1A transcripts resulted in reduced growth of cancer cells in vitro and in nude mice supporting a role for RASSF1A as a tumor suppressor gene. Since, the restoration of RASSF1A expression in tumor cells impairs their tumorigenicity, factors that restore RASSF1A expression have immense importance in preventing tumor growth. For long time epidemiological studies have suggested that plant derived bioactive compounds might have enormous benefit in preventing various cancers in human. In a recent study we evaluated a plant alkaloid, mahanine, isolated and purified from M. koenigii, in human prostate cancer cells and demonstrated growth inhibition in both androgen-responsive, LNCaP and androgen-independent, PC3 cells. In preliminary study, we observed that mahanine restores RASSF1A expression in human and mouse prostate cancer cells and down-regulates cyclin D1 expression. Therefore, the specific aims of this project are: 1) to determine the in vivo efficacy of mahanine in regulation of prostate cancer growth, the development of poorly-differentiated prostate cancer will be examined in TRAMP model with or without mahanine treatments. In addition, to determine the therapeutic potential of mahanine, growth inhibition of already established human prostate tumor in nude mice will be examined. Moreover, to assess mahanine is safe to use, a detailed toxicity test will be performed. 2) to determine the mechanism by which mahanine re-expresses RASSF1A in prostate cancer cells, the methylation status of RASSF1A promoter will be examined in vitro and in vivo with or without mahanine treatments. Moreover, the role of DNA methyltransferases (DNMT1, 3a and 3b) in re-expression of RASSF1A in prostate cancer cells by mahanine will be examined. 3) Finally, to determine the molecular mechanism of mahanine-induced down-regulation of cyclin D1, role of RASSF1A in inhibition of cyclin D1 will be examined. This study will demonstrate whether mahanine-induced RASSF1A regulates cyclin D1 transcriptionally via the CREB, and/or whether RASSF1A regulates cyclin D1 post-transcriptionally via the Akt. This project will provide a better understanding about the efficacy of mahanine in preventing and/or intervening prostate cancer growth in vivo and the underlying mechanisms for growth inhibition by mahanine which is crucial for future therapeutic intervention of prostate cancer in human.